This invention relates to compositions of hydrogenated block copolymers.
Partially hydrogenated block copolymers of vinyl aromatic and conjugated dienes such as hydrogenated styrene-butadiene-styrene copolymers are well known in the art. U.S. Pat. Nos. 3,333,024; 3,431,323; 3,598,886; 5,352,744; 3,644,588 and EP-505,110 disclose various hydrogenated block copolymers. Partially hydrogenated refers to hydrogenation of the diene portion of the block copolymer without aromatic hydrogenation or aromatic hydrogenation of 90 percent or less. Although these partially hydrogenated copolymers have been tested in various applications, they suffer from one or more shortcomings, including low heat resistance, poor physical properties, poor processability, low heat resistance and poor light stability. Attempts have been made to remedy these shortcomings by increasing the hydrogenation of the aromatic ring of the block copolymer. However, polymer scientists contend that fully hydrogenated styrene-butadiene-styrene copolymers have no useful properties at elevated temperatures, even if only slightly elevated. Thermoplastic Elastomers, 2nd edition, 1996, page 304, lines 8-12 states xe2x80x9cThus, polystyrene remains the choice for any amorphous hydrocarbon block copolymer. This last fact is clearly demonstrated in the case of the fully hydrogenated VCH-EB-VCH polymer. The interaction parameter is so severely reduced by hydrogenation that at only slightly elevated temperatures, the polymer loses all strength and appears to be homogeneously mixed at ordinary melt temperatures.xe2x80x9d
Specifically, hydrogenated diblock copolymers tend to have low viscosities and melt strengths making them difficult to process. Diblocks also have other disadvantages due to their poor tensile properties. For the same reason they are not useful for making flexible materials, while rigid materials made from diblocks tend to be brittle.
Blends of partially hydrogenated block copolymers with other polymers are also known. For example, blends of cyclic olefin (co)polymers have been attempted as disclosed in EP-0726291, wherein cyclic olefin (co)polymers are blended with vinyl aromatic/conjugated diene block copolymers or hydrogenated versions thereof. Cyclic olefin (co)polymers (COC""s) are known to have excellent heat distortion temperature, UV stability and processability. However, such copolymers suffer from poor impact resistance. Blends of COC""s with partially hydrogenated block copolymers still suffer from an imbalance of physical properties due to the absence of aromatic hydrogenation within the block copolymer.
Therefore, there remains a need for compositions of fully or substantially hydrogenated block copolymers which have adequate viscosity and melt strength to ease processability, can be used in elastomeric applications and have a desirable balance of physical properties.
Additionally, uses for clear, substantially or fully hydrogenated hydrogenated block copolymers of vinyl aromatic and conjugated diene monomers, and polymer blends thereof, are still desired, wherein the copolymers are processable by conventional manufacturing technologies and possess useful physical properties at standard and elevated temperatures.
One aspect of the present invention is directed to compositions comprising fully or substantially hydrogenated block copolymers and various end-use applications thereof. The hydrogenated block copolymer is a rigid hydrogenated block copolymer, which comprises at least two distinct blocks of hydrogenated polymerized vinyl aromatic monomer, herein referred to as hydrogenated vinyl aromatic polymer blocks, and at least one block of hydrogenated polymerized conjugated diene monomer, herein referred to as hydrogenated conjugated diene polymer block, wherein the hydrogenated copolymer is further characterized by:
a) a weight ratio of hydrogenated conjugated diene polymer block to hydrogenated vinyl aromatic polymer block of 40:60 or less;
b) a total number average molecular weight (Mnt) of from 30,000 to 150,000, wherein each hydrogenated vinyl aromatic polymer block (A) has a Mna of from 6,000 to 60,000 and each hydrogenated conjugated diene polymer block (B) has a Mnb of from 3,000 to 30,000; and
c) a hydrogenation level such that each hydrogenated vinyl aromatic polymer block has a hydrogenation level of greater than 90 percent and each hydrogenated conjugated diene polymer block has a hydrogenation level of greater than 95 percent.
Hydrogenated block copolymers having these Mn and hydrogenation characteristics are transparent to light at visible wavelengths and are ideally suited for various applications, while possessing excellent properties at both standard and elevated temperatures. The combination of transparency, high glass transition temperature, low water absorption, good strength, toughness, weatherability and excellent melt processability makes these materials and blends thereof, ideal candidates for many applications including fabricated articles, thermoformed articles, extruded articles, injection molded articles, films and the like.
One aspect of the present invention is directed to applications for rigid hydrogenated block copolymers and end-use applications thereof. Hydrogenated block copolymers are prepared by hydrogenating a block copolymer produced from a vinyl aromatic monomer and a conjugated diene monomer.
The vinyl aromatic monomer is typically a monomer of the formula 
wherein Rxe2x80x2 is hydrogen or alkyl, Ar is phenyl, halophenyl, alkylphenyl, alkylhalophenyl, naphthyl, pyridinyl, or anthracenyl, wherein any alkyl group contains 1 to 6 carbon atoms which may be mono or multisubstituted with functional groups such as halo, nitro, amino, hydroxy, cyano, carbonyl and carboxyl. More preferably Ar is phenyl or alkyl phenyl with phenyl being most preferred. Typical vinyl aromatic monomers include styrene, alpha-methylstyrene, all isomers of vinyl toluene, especially paravinyltoluene, all isomers of ethyl styrene, propyl styrene, butyl styrene, vinyl biphenyl, vinyl naphthalene, vinyl anthracene and the like, and mixtures thereof. The block copolymer can contain more than one specific polymerized vinyl aromatic monomer. In other words, the block copolymer can contain a polystyrene block and a poly-alpha-methylstyrene block. The hydrogenated vinyl aromatic polymer block can also be a copolymer wherein the hydrogenated vinyl aromatic component is at least 50 weight percent of the copolymer.
The conjugated diene monomer can be any monomer having 2 conjugated double bonds. Such monomers include for example 1,3-butadiene, 2-methyl-1,3-butadiene, 2-methyl-1,3 pentadiene, isoprene and similar compounds, and mixtures thereof. The block copolymer can contain more than one specific polymerized conjugated diene monomer. In other words, the block copolymer can contain a polybutadiene block and a polyisoprene block.
The conjugated diene polymer block can be prepared from materials which remain amorphous after the hydrogenation process, or materials which are capable of crystallization after hydrogenation. Hydrogenated polyisoprene blocks remain amorphous, while hydrogenated polybutadiene blocks can be either amorphous or crystallizable depending upon their structure. Polybutadiene can contain either a 1,2 configuration, which hydrogenates to give the equivalent of a 1-butene repeat unit, or a 1,4-configuration, which hydrogenates to give the equivalent of an ethylene repeat unit. Polybutadiene blocks having at least approximately 40 weight percent 1,2-butadiene content, based on the weight of the polybutadiene block, provides substantially amorphous blocks with low glass transition temperatures upon hydrogenation. Polybutadiene blocks having less than approximately 40 weight percent 1,2-butadiene content, based on the weight of the polybutadiene block, provide crystalline blocks upon hydrogenation. Depending on the final application of the polymer it may be desirable to incorporate a crystalline block (to improve solvent resistance) or an amorphous, more compliant block. In some applications, the block copolymer can contain more than one conjugated diene polymer block, such as a polybutadiene block and a polyisoprene block. The conjugated diene polymer block may also be a copolymer of a conjugated diene, wherein the conjugated diene portion of the copolymer is at least 50 weight percent of the copolymer. The conjugated diene polymer block may also be a copolymer of more than one conjugated diene, such as a copolymer of butadiene and isoprene.
Other polymeric blocks may also be included in the hydrogenated block copolymers of the present invention.
A block is herein defined as a polymeric segment of a copolymer which exhibits microphase separation from a structurally or compositionally different polymeric segment of the copolymer. Microphase separation occurs due to the incompatibility of the polymeric segments within the block copolymer. Microphase separation and block copolymers are widely discussed in xe2x80x9cBlock Copolymers-Designer Soft Materialsxe2x80x9d, PHYSICS TODAY, February, 1999, pages 32-38.
The rigid hydrogenated block copolymers are defined as having a weight ratio of hydrogenated conjugated diene polymer block to hydrogenated vinyl aromatic polymer block of 40:60 or less, typically from 40:60 to 5:95, preferably from 35:65 to 10:90, more preferably from 30:70 to 15:85, based on the total weight of the hydrogenated conjugated diene polymer block and the hydrogenated vinyl aromatic polymer block. The total weights of the hydrogenated vinyl aromatic polymer blocks and the hydrogenated conjugated diene polymer block(s) is typically at least 80 weight percent, preferably at least 90, and more preferably at least 95 weight percent of the total weight of the hydrogenated copolymer.
The rigid hydrogenated block copolymers used in the present invention are produced by the hydrogenation of block copolymers including triblock, multiblock, tapered block, and star block copolymers such as SBS, SBSBS, SIS, SISIS, SISBS and the like (wherein S is polystyrene, B is polybutadiene and I is polyisoprene). The block copolymers contain at least one triblock segment comprised of a vinyl aromatic polymer block on each end. The block copolymers may, however, contain any number of additional blocks, wherein these blocks may be attached at any point to the triblock polymer backbone. Thus, linear blocks would include for example SBS, SBSB, SBSBS, SBSBSB, and the like. The copolymer can also be branched, wherein polymer chains are attached at any point along the copolymer backbone. It should be noted here that in the production of block copolymers, it is expected that small amounts of residual diblock copolymers are also produced.
The total number average molecular weight (Mnt) of the rigid hydrogenated block copolymers used in the present invention is typically from 24,000, preferably from 30,000, more preferably from 45,000 and most preferably from 50,000 to 150,000, typically to 135,000, generally to 115,000, preferably to 100,000, more preferably to 90,000, and most preferably to 85,000. The Mn, as referred to throughout this specification, is determined by gel permeation chromatography (GPC). The molecular weight of the rigid hydrogenated block copolymer and properties obtained are dependent upon the molecular weight of each of the hydrogenated polymeric blocks.
Number average molecular weight (Mn) and weight average molecular weight (Mw) can both be used to describe the polymers described herein. Because these polymers tend to have very narrow molecular weight polydispersities, the difference between Mn and Mw will be minimal. The ratio of Mw to Mn is typically 1.1 or less. In fact, in some cases the number average molecular weight and the number average molecular weight will be virtually the same. Therefore, Mn can also be read as Mw throughout this application.
It should be noted that good properties are obtained at hydrogenated vinyl aromatic polymer molecular weights which are lower than the entanglement molecular weight of the hydrogenated vinyl aromatic polymer. The entanglement molecular weight of a polymer is associated with the chain length required for a given polymer to show a dramatic increase in melt viscosity due to chain entanglements. The entanglement molecular weights for many common polymers have been measured and reported in Macromolecules, 1994, Volume 27, page 4639. It is commonly observed for glassy polymers that maximum values of strength and toughness are achieved at about 10 times the entanglement molecular weight (see, for instance, Styrene Polymers in the Encyclopedia of Polymer Science and Engineering, 2nd edition, Volume 16, pages 62-71, 1989). The entanglement molecular weight is approximately 38,000 for hydrogenated polystyrene (polyvinylcyclohexane). We have determined that an optimum balance of properties and processability can be obtained at hydrogenated vinyl aromatic polymer block molecular weights (Mn) of 0.2 to 1.2 times the entanglement molecular weight of a hydrogenated vinyl aromatic polymer.
The Mna of the rigid hydrogenated vinyl aromatic polymer block will typically be from 6,000, preferably from 10,000, more preferably from 15,000 and most preferably from 20,000 to 60,000, preferably to 50,000, more preferably to 45,000 and most preferably to 40,000. The hydrogenated diene polymer block will typically have a Mnb from 4,000, preferably from 8,000, more preferably from 10,000, and most preferably from 12,000 to 30,000, preferably to 28,000, most preferably to 25,000 and most preferably to 22,000.
It is important to note that each individual block of the rigid hydrogenated block copolymer of the present invention, can have its own distinct Mn. In other words, for example, two hydrogenated vinyl aromatic polymer blocks within the hydrogenated block copolymer may each have a different Mn.
Methods of making block copolymers are well known in the art. Typically, block copolymers are made by anionic polymerization, examples of which are cited in Anionic Polymerization: Principles and Practical Applications, H. L. Hsieh and R. P. Quirk, Marcel Dekker, New York, 1996. In one embodiment, block copolymers are made by sequential monomer addition to a carbanionic initiator such as sec-butyl lithium or n-butyl lithium. In another embodiment, the copolymer is made by coupling a triblock material with a divalent coupling agent such as 1,2-dibromoethane, dichlorodimethylsilane, or phenylbenzoate. In this embodiment, a small chain (less than 10 monomer repeat units) of a conjugated diene polymer can be reacted with the vinyl aromatic polymer coupling end to facilitate the coupling reaction. Vinyl aromatic polymer blocks are typically difficult to couple, therefore, this technique is commonly used to achieve coupling of the vinyl aromatic polymer ends. The small chain of diene polymer does not constitute a distinct block since no microphase separation is achieved. Coupling reagents and strategies which have been demonstrated for a variety of anionic polymerizations are discussed in Hsieh and Quirk, Chapter 12, pgs. 307-331. In another embodiment, a difunctional anionic initiator is used to initiate the polymerization from the center of the block system, wherein subsequent monomer additions add equally to both ends of the growing polymer chain. An example of a such a difunctional initiator is 1,3-bis(1-phenylethenyl) benzene treated with organolithium compounds, as described in U.S. Pat. Nos. 4,200,718 and 4,196,154 which are herein incorporated by reference.
After preparation of the block copolymer, the copolymer is hydrogenated to remove sites of unsaturation in both the conjugated diene polymer block and the vinyl aromatic polymer block segments of the copolymer. Any method of hydrogenation can be used and such methods typically include the use of metal catalysts supported on an inorganic substrate, such as Pd on BaSO4 (U.S. Pat. No. 5,352,744) and Ni on kieselguhr (U.S. Pat. No. 3,333,024) both of which are incorporated herein by reference. Additionally, soluble, homogeneous catalysts such those prepared from combinations of transition metal salts of 2-ethylhexanoic acid and alkyl lithiums can be used to fully saturate block copolymers, as described in Die Makromolekulare Chemie, Volume 160, pp. 291, 1972. The copolymer hydrogenation can also be achieved using hydrogen and a heterogeneous catalyst such as those described in U.S. Pat. Nos. 5,352,744, 5,612422 and 5,645,253 which are herein incorporated by reference. The catalysts described therein are heterogeneous catalysts consisting of a metal crystallite supported on a porous silica substrate. An example of a silica supported catalyst which is especially useful in the polymer hydrogenation is a silica which has a surface area of at least 10 m2/g which is synthesized such that is contains pores with diameters ranging between 3000 and 6000 angstroms. This silica is then impregnated with a metal capable of catalyzing hydrogenation of the polymer, such as nickel, cobalt, rhodium, ruthenium, palladium, platinum, other Group VIII metals, combinations or alloys thereof. Other heterogeneous catalysts can also be used, having diameters in the range of 500 to 3,000 angstroms.
Alternatively, the hydrogenation can be conducted in the presence of a mixed hydrogenation catalyst characterized in that it comprises a mixture of at least two components. The first component comprises any metal which will increase the rate of hydrogenation and includes nickel, cobalt, rhodium, ruthenium, palladium, platinum, other Group VIII metals, or combinations thereof. Preferably rhodium and/or platinum is used. The second component used in the mixed hydrogenation catalyst comprises a promoter which inhibits deactivation of the Group VIII metal(s) upon exposure to polar materials, and is herein referred to as the deactivation resistant component. Such components preferably comprise rhenium, molybdenum, tungsten, tantalum or niobium or mixtures thereof.
The amount of the deactivation resistant component in the mixed catalyst is at least an amount which significantly inhibits the deactivation of the Group VIII metal component when exposed to polar impurities within a polymer composition, herein referred to as a deactivation inhibiting amount. Deactivation of the Group VIII metal is evidenced by a significant decrease in hydrogenation reaction rate. This is exemplified in comparisons of a mixed hydrogenation catalyst and a catalyst containing only a Group VIII metal component under identical conditions in the presence of a polar impurity, wherein the catalyst containing only a Group VIII metal component exhibits a hydrogenation reaction rate which is less than 75 percent of the rate achieved with the mixed hydrogenation catalyst.
Preferably, the amount of deactivation resistant component is such that the ratio of the Group VIII metal component to the deactivation resistant component is from 0.5:1 to 10:1, more preferably from 1:1 to 7:1, and most preferably from 1:1 to 5:1.
The mixed catalyst can consist of the components alone, but preferably the catalyst additionally comprises a support on which the components are deposited. In one embodiment, the metals are deposited on a support such as a silica, alumina or carbon. In a more specific embodiment, a silica support having a narrow pore size distribution and surface area greater than 10 meters squared per gram (m2/g) is used.
The pore size distribution, pore volume, and average pore diameter of the support can be obtained via mercury porosimetry following the proceedings of ASTM D-4284-83.
The pore size distribution is typically measured using mercury porosimetry. However, this method is only sufficient for measuring pores of greater than 60 angstroms. Therefore, an additional method must be used to measure pores less than 60 angstroms. One such method is nitrogen desorption according to ASTM D-4641-87 for pore diameters of less than about 600 angstroms. Therefore, narrow pore size distribution is defined as the requirement that at least 98 percent of the pore volume is defined by pores having pore diameters greater than 300 angstroms and that the pore volume measured by nitrogen desorption for pores less than 300 angstroms, be less than 2 percent of the total pore volume measured by mercury porosimetry.
The surface area can be measured according to ASTM D-3663-84. The surface area is typically between 10 and 100 m2/g, preferably between 15 and 90 with most preferably between 50 and 85 m2/g.
The desired average pore diameter of the support for the mixed catalyst is dependent upon the polymer which is to be hydrogenated and its molecular weight. It is preferable to use supports having higher average pore diameters for the hydrogenation of polymers having higher molecular weights to obtain the desired amount of hydrogenation. For high molecular weight polymers (Mn greater than 200,000 for example), the typical desired surface area can vary from 15 to 25 m2/g and the desired average pore diameter from 3,000 to 4000 angstroms. For lower molecular weight polymers (Mn less than 100,000 for example), the typical desired surface area can vary from 45 to 85 m2/g and the desired average pore diameter from 300 to 700 angstroms.
Silica supports are preferred and can be made by combining potassium silicate in water with a gelation agent, such as formamide, polymerizing and leaching as exemplified in U.S. Pat. No. 4,112,032. The silica is then hydrothermally calcined as in Iler, R. K., The Chemistry of Silica, John Wiley and Sons, 1979, pp. 539-544, which generally consists of heating the silica while passing a gas saturated with water over the silica for about 2 hours or more at temperatures from about 600xc2x0 C. to about 850xc2x0 C. Hydrothermal calcining results in a narrowing of the pore diameter distribution as well as increasing the average pore diameter. Alternatively, the support can be prepared by processes disclosed in Iler, R. K., The Chemistry of Silica, John Wiley and Sons, 1979, pp. 510-581.
A silica supported catalyst can be made using the process described in U.S. Pat. No. 5,110,779, which is incorporated herein by reference. An appropriate metal, metal component, metal containing compound or mixtures thereof, can be deposited on the support by vapor phase deposition, aqueous or nonaqueous impregnation followed by calcination, sublimation or any other conventional method, such as those exemplified in Studies in Surface Science and Catalysis, xe2x80x9cSuccessful Design of Catalystsxe2x80x9d V. 44, pg. 146-158, 1989 and Applied Heterogeneous Catalysis pgs. 75-123, Institute Franxc3xa7ais du Pxc3xa9trole Publications, 1987. In methods of impregnation, the appropriate metal containing compound can be any compound containing a metal, as previously described, which will produce a usable hydrogenation catalyst which is resistant to deactivation. These compounds can be salts, coordination complexes, organometallic compounds or covalent complexes.
Typically, the total metal content of the mixed supported catalyst is from 0.1 to 10 wt. percent based on the total weight of the silica supported catalyst. Preferable amounts are from 2 to 8 wt. percent, more preferably 0.5 to 5 wt. percent based on total catalyst weight.
Promoters, such as alkali, alkali earth or lanthanide containing compounds, can also be used to aid in the dispersion of the metal component onto the silica support or stabilization during the reaction, though their use is not preferred.
The amount of mixed supported catalyst used in the hydrogenation process is much smaller than the amount required in conventional unsaturated polymer hydrogenation reactions due to the high reactivity of the hydrogenation catalysts. Generally, amounts of less than 1 gram of supported catalyst per gram of unsaturated polymer are used, with less than 0.1 gram being preferred and less than 0.05 being more preferred. The amount of supported catalyst used is dependent upon the type of process, whether it is continuous, semi-continuous or batch, and the process conditions, such as temperature, pressure and reaction time wherein typical reaction times may vary from about 5 minutes to about 5 hours. Continuous operations can typically contain 1 part by weight supported catalyst to 200,000 or more parts unsaturated polymer, since the supported catalyst is reused many times during the course of continuous operation. Typical batch processes can use 1 part by weight supported catalyst to 5,000 parts unsaturated polymer. Higher temperatures and pressures will also enable using smaller amounts of supported catalyst.
The hydrogenation reaction can be conducted in the absence of a solvent but is preferably conducted in a hydrocarbon solvent in which the polymer is soluble and which will not hinder the hydrogenation reaction. Preferably the solvent is a saturated solvent such as cyclohexane, methylcyclohexane, ethylcyclohexane, cyclooctane, cycloheptane, dodecane, dioxane, diethylene glycol dimethyl ether, tetrahydrofuran, isopentane, decahydronaphthalene or mixtures thereof, with cyclohexane being the most preferred.
Typical hydrogenation temperatures are from about 40xc2x0 C. preferably from about 100xc2x0 C., more preferably from about 200xc2x0 C., and most preferably from about 120xc2x0 C. to about 250xc2x0 C., preferably to about 200xc2x0 C., more preferably to about 180xc2x0 C., and most preferably to about 170xc2x0 C.
The pressure of the hydrogenation reaction is not critical, though hydrogenation rates increase with increasing pressure. Typical pressures range from atmospheric pressure to 70 MPa, with 0.7 to 10.3 MPa being preferred.
The reaction vessel is purged with an inert gas to remove oxygen from the reaction area. Inert gases include but are not limited to nitrogen, helium, and argon, with nitrogen being preferred.
The hydrogenating agent can be any hydrogen producing compound which will efficiently hydrogenate the unsaturated polymer. Hydrogenating agents include but are not limited to hydrogen gas, hydrazine and sodium borohydride. In a preferred embodiment, the hydrogenating agent is hydrogen gas.
Hydrogenated rigid block copolymers used in the present invention are also defined as being substantially or fully hydrogenated in that at least 90 percent of the aromatic rings of the block copolymer are hydrogenated, and may be referred to as substantially hydrogenated rigid block copolymers. The level of hydrogenation is preferably greater than 95 percent of the conjugated diene polymer block and greater than 90 percent of the vinyl aromatic polymer block segments, more preferably greater than 99 percent of the conjugated diene polymer block and greater than 95 percent of the vinyl aromatic polymer block segments, even more preferably greater than 99.5 percent of the conjugated diene polymer block and greater than 98 percent of the vinyl aromatic polymer block segments, and most preferably greater than 99.9 percent of the conjugated diene polymer block and 99.5 percent of the vinyl aromatic polymer block segments. The term xe2x80x98level of hydrogenationxe2x80x99 refers to the percentage of the original unsaturated bonds which become saturated upon hydrogenation. The level of hydrogenation in hydrogenated vinyl aromatic polymers is determined using UV-VIS spectrophotometry, while the level of hydrogenation in hydrogenated diene polymers is determined using proton NMR.
Anionically polymerized block copolymers typically microphase separate into well-defined morphologies, with morphology dimensions typically ranging from 5 to 50 nanometers in size. Typical morphologies include a continuous matrix phase of one hydrogenated polymer with well-defined spheres, cylinders or gyroids of the minor phase hydrogenated polymer blocks dispersed within the matrix, and a lamellar cocontinuous phase, wherein both hydrogenated polymer blocks are in a continuous phase interspersed within each other. These different morphologies give rise to different physical properties. Hydrogenated block copolymers in which the hydrogenated conjugated diene polymer blocks are continuous are typically elastomeric, highly resilient materials. Conversely, materials in which the hydrogenated vinyl aromatic polymer block segments are the continuous phase are typically stiff, tough plastics. Hydrogenated block copolymers wherein both hydrogenated polymer blocks are cocontinuous tend to have intermediate properties.
In one embodiment, the composition comprises a hydrogenated block copolymer comprising less than 80 weight percent hydrogenated vinyl aromatic polymer blocks, based on the total weight of the hydrogenated block copolymer, and has an aromatic hydrogenation level of greater than 90 percent.
In another embodiment, the composition comprises a hydrogenated block copolymer of a vinyl aromatic and a conjugated diene, wherein the block copolymer is a pentablock copolymer comprising 3 blocks of hydrogenated vinyl aromatic polymer and two blocks of conjugated diene polymer. The hydrogenated pentablock copolymer comprises less than 80 weight percent hydrogenated vinyl aromatic polymer blocks, based on the total weight of the hydrogenated block copolymer, and has an aromatic hydrogenation level of greater than 90 percent.
Another aspect of the present invention relates to polymer blends of the hydrogenated rigid block copolymers.
Compositions comprising hydrogenated rigid block copolymer (or substantially hydrogenated rigid block copolymer), may also comprise at least one other natural or synthetic polymer. Suitable polymeric materials include, but are not limited to, hydrogenated vinyl aromatic homopolymers, other hydrogenated block copolymers, including hydrogenated styrene/butadiene or styrene/isoprene block copolymers, thermoplastic polyurethanes, polycarbonates (PC), polyamides, polyethers, poly/vinyl chloride polymers, poly/vinylidene chloride polymers, polyesters, polymers that contain lactic acid residuals, partially or non-hydrogenated block copolymers, thermoplastics such as styrene-butadiene block copolymers, polystyrene (including high impact polystyrene), acrylonitrile-butadiene-styrene (ABS) copolymers, styrene-acrylonitrile copolymers (SAN), ABS/PC compositions, polyethylene terephthalate, epoxy resins, ethylene vinyl alcohol copolymers, ethylene acrylic acid copolymers, polyolefin carbon monoxide interpolymers, chlorinated polyethylene, cyclic olefin copolymers (COC""s), olefin copolymers (especially polyethylene copolymers such as ethylene-styrene interpolymers) and homopolymers (e.g., those made using conventional heterogeneous catalysts). Examples include polymers made by the process of U.S. Pat. No. 4,076,698, incorporated herein by reference.
In one embodiment, the composition additionally comprises a polyolefin elastomer or plastomer, especially a polyolefin elastomer or plastomer made using a single-site catalyst system (for example, a homogeneously branched ethylene polymer such as a substantially linear ethylene interpolymer or a homogeneously branched linear ethylene interpolymer).
Generally suitable polyolefins include, for example, polyethylene (ethylene homopolymer), ethylene/alpha-olefin interpolymers, alpha-olefin homopolymers, such as polypropylene(propylene homopolymer), alpha-olefin interpolymers, such as interpolymers of polypropylene and an alpha-olefin having at least 4 carbon atoms.
Representative polyolefins include, for example, but are not limited to, substantially linear ethylene polymers, homogeneously branched linear ethylene polymers, heterogeneously branched linear ethylene (including linear low density polyethylene (LLDPE), ultra or very low density polyethylene (ULDPE or VLDPE) medium density polyethylene (MDPE) and high density polyethylene (HDPE)), high pressure low density polyethylene (LDPE), ethylene/acrylic acid (EAA) copolymers, ethylene/methacrylic acid (EMAA) copolymers, ethylene/acrylic acid (EAA) ionomers, ethylene/methacrylic acid (EMAA) ionomers, ethylene/vinyl acetate (EVA) copolymers, ethylene/vinyl alcohol (EVOH) copolymers, polypropylene homopolymers and copolymers, ethylene/propylene polymers, ethylene/styrene interpolymers, graft-modified polymers (e.g., maleic anhydride grafted polyethylene such as LLDPE g-MAH), ethylene acrylate copolymers (e.g. ethylene/ethyl acrylate (EEA) copolymers, ethylene/methyl acrylate (EMA), and ethylene/methmethyl acrylate (EMMA) copolymers), polybutylene (PB), ethylene carbon monoxide interpolymer (e.g., ethylene/carbon monoxide (ECO), copolymer, ethylene/acrylic acid/carbon monoxide (EAACO) terpolymer, ethylene/methacrylic acid/carbon monoxide (EMAACO) terpolymer, ethylene/vinyl acetate/carbon monoxide (EVACO) terpolymer and styrene/carbon monoxide (SCO), chlorinated polyethylene and mixtures thereof.
Ethylene/styrene interpolymers are prepared by polymerizing i) ethylene or one or more alpha-olefin monomers and ii) one or more vinyl or vinylidene aromatic monomers and/or one or more sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene monomers, and optionally iii) other polymerizable ethylenically unsaturated monomer(s).
Ethylene/styrene interpolymers can be substantially random, psuedo-random, random, alternately, diadic, triadic, tetradic or any combination thereof. That is, the interpolymer product can be variably incorporated and optionally variably sequenced. Preferred ethylene/styrene interpolymers are substantially random ethylene/styrene interpolymers.
The term xe2x80x9cvariably incorporatedxe2x80x9d as used herein refers to a ethylene/styrene interpolymer manufactured using at least two catalyst systems wherein during interpolymerization the catalyst systems are operated at different incorporation or reactivity rates. For example, the interpolymer product having a total styrene content of 36 weight percent is variably incorporated where one catalyst system incorporates 22 weight percent styrene and the other catalyst system incorporates 48 weight percent styrene and the production split between the two catalyst systems is 47/53 weight percentages.
xe2x80x9cPseudo-randomxe2x80x9d ethylene/styrene interpolymers are described in U.S. Pat. No. 5,703,187, the disclosure of which is incorporated herein in its entirety by reference.
xe2x80x9cRandomxe2x80x9d interpolymers are those in which the monomer units are incorporated into the chain wherein there can exist various combinations of ordering including blockiness where either the aliphatic alpha-olefin monomer (A) or hindered vinylidene monomer (B) or both can be repeated adjacent to one another.
xe2x80x9cAlternatingxe2x80x9d ethylene/styrene interpolymers are those in which the aliphatic alpha-olefin monomer (A) and hindered vinylidene monomer (B) occur in repeat alternate sequences on the polymer chain in atactic or stereospecific structures (such as isotactic or syndiotactic) or in combinations of the general formula (AB)n, wherein n is an integer from 1 to 4000. The term xe2x80x9csubstantially randomxe2x80x9d as used herein in reference to ethylene/styrene interpolymers generally means that the distribution of the monomers of the interpolymer can be described by the Bernoulli statistical model or by a first or second order Markovian statistical model, as described by J. C. Randall in POLYMER SEQUENCE DETERMINATION, Carbon-13 NMR Method, Academic Press New York, 1977, pp. 71-78. Substantially random interpolymers do not contain more than 15 mole percent of the total amount of vinyl or vinylidene aromatic monomer in blocks of vinyl or vinylidene aromatic monomer of more than 3 units.
Preferably, the substantially random interpolymer is not characterized by a high degree (greater than 50 mol %) of either isotacticity or syndiotacticity. This means that in the carbonxe2x88x9213 NMR spectrum of the substantially random interpolymer, the peak areas corresponding to the main chain methylene and methine carbons representing either meso diad sequences or racemic diad sequences should not exceed 75 percent of the total peak area of the main chain methylene and methine carbons. By the subsequently used term xe2x80x9csubstantially random interpolymerxe2x80x9d it is meant a substantially random interpolymer produced from the above-mentioned monomers.
Suitable xcex1-olefin monomers which are useful for preparing the substantially random ethylene/styrene interpolymer include, for example, xcex1-olefin monomers containing from about 2 to about 20, preferably from about 2 to about 12, more preferably from about 2 to about 8 carbon atoms. Preferred such monomers include ethylene, propylene, butene-1,4-methyl-1-pentene, hexene-1 and octene-1. Most preferred are ethylene or a combination of ethylene with C3-C8 xcex1-olefins. These xcex1 olefins do not contain an aromatic moiety.
Suitable vinyl or vinylidene aromatic monomers which can be employed to prepare the substantially random ethylene/styrene interpolymer include, for example, those represented by the following formula: 
wherein R1 is selected from the group of radicals consisting of hydrogen and alkyl radicals containing from about 1 to about 4 carbon atoms, preferably hydrogen or methyl; each R2 is independently selected from the group of radicals consisting of hydrogen and alkyl radicals containing from about 1 to about 4 carbon atoms, preferably hydrogen or methyl; Ar is a phenyl group or a phenyl group substituted with from about 1 to about 5 substituents selected from the group consisting of halo, C1-4-alkyl, and C1-4-haloalkyl; and n has a value from zero to about 4, preferably from zero to about 2, most preferably zero. Particularly suitable such monomers include styrene and lower alkyl- or halogen-substituted derivatives thereof. Exemplary monovinyl or monovinylidene aromatic monomers include styrene, vinyl toluene, xcex1-methylstyrene, t-butyl styrene or chlorostyrene, including all isomers of these compounds. Preferred monomers include styrene, (xcex1-methyl styrene, the lower alkyl-(C1-C4) or phenyl-ring substituted derivatives of styrene, such as for example, ortho-, meta-, and para-methylstyrene, the ring halogenated styrenes, para-vinyl toluene or mixtures thereof. A more preferred aromatic monovinyl monomer is styrene.
By the term xe2x80x9csterically hindered aliphatic or cycloaliphatic vinyl or vinylidene monomersxe2x80x9d in reference to substantially random ethylene/styrene interpolymers, it is meant addition polymerizable vinyl or vinylidene monomers corresponding to the formula: 
wherein A1 is a sterically bulky, aliphatic or cycloaliphatic substituent of up to 20 carbons, R1 is selected from the group of radicals consisting of hydrogen and alkyl radicals containing from about 1 to about 4 carbon atoms, preferably hydrogen or methyl; each R2 is independently selected from the group of radicals consisting of hydrogen and alkyl radicals containing from about 1 to about 4 carbon atoms, preferably hydrogen or methyl; or alternatively R1 and A1 together form a ring system.
By the term xe2x80x9csterically bulkyxe2x80x9d as used in reference to substantially random ethylene/styrene interpolymers it is meant that the monomer bearing this substituent is normally incapable of addition polymerization by standard Ziegler-Natta polymerization catalysts at a rate comparable with ethylene polymerizations.
xcex1-Olefin monomers containing from about 2 to about 20 carbon atoms and having a linear aliphatic structure such as ethylene, propylene, butene-1, hexene-1 and octene-1 are not considered to be sterically hindered aliphatic monomers. With regard to substantially random ethylene/styrene interpolymer, preferred sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene compounds are monomers in which one of the carbon atoms bearing ethylenic unsaturation is tertiary or quaternary substituted. Examples of such substituents include cyclic aliphatic groups such as cyclohexyl, cyclohexenyl, cyclooctenyl, or ring alkyl or aryl substituted derivatives thereof, tert-butyl or norbornyl. Most preferred sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene compounds are the various isomeric vinyl-ring substituted derivatives of cyclohexene and substituted cyclohexenes, and 5-ethylidene-2-norbornene. Especially suitable are 1-, 3-, and 4-vinylcyclohexene.
The substantially random ethylene/styrene interpolymer usually contains from about 5 to about 65, preferably from about 5 to about 55, more preferably from about 10 to about 50 mole percent of at least one vinyl or vinylidene aromatic monomer; or sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene monomer; or both; and from about 35 to about 95, preferably from about 45 to about 95, more preferably from about 50 to about 90 mole percent of at least one aliphatic xcex1-olefin having from about 2 to about 20 carbon atoms.
Other optional polymerizable ethylenically unsaturated monomer(s) for substantially random ethylene/styrene interpolymers include strained ring olefins such as norbornene and C1-C10-alkyl or C6-C10-aryl substituted norbornene, with an exemplary substantially random interpolymer being ethylene/styrene/norbornene.
A preferred polymeric material for blending with a rigid hydrogenated block copolymer is a polyolefin elastomer or plastomer characterized as having a DSC crystallinity of less than 45 weight percent, preferably less than 30 weight percent, more preferably less than or equal to 20 weight percent, and most preferably less than or equal 16 percent.
The polyolefin elastomer or plastomer will typically be characterized as having a melt index of less than 1000 g/10 minutes, preferably less than 500 g/10 minutes, most preferably less than or equal to 50 g/10 minutes, as determined in accordance with ASTM D-1238, Condition 190xc2x0 C./2.16 kilogram (kg). However, in certain embodiments, it will be desirable to utilize an ultra-low molecular weight polyolefin elastomer or plastomer. In particular, ultra-low molecular weight ethylene polymers, such as are disclosed in U.S. Pat. No. 6,054,544, may find utility in the practice of the claimed invention.
The ultra-low molecular weight ethylene polymers useful in the practice of the invention will be characterized as having a melt viscosity at 350xc2x0 F. of less than 8200, preferably less than 6000, with melt viscosities at 350xc2x0 F. of less than 600 centipoise being easily attained. The melt viscosity will be chosen based on the desired result. In particular, the lower the melt viscosity of the ultra-low molecular weight ethylene polymer, the more it will tend to reduce the overall viscosity of the compositions of the invention.
Melt viscosity is determined in accordance with the following procedure using a Brookfield Laboratories DVII+ Viscometer in disposable aluminum sample chambers. The spindle used is a SC-31 hot-melt spindle, suitable for measuring viscosities in the range of from 10 to 100,000 centipoise. A cutting blade is employed to cut samples into pieces small enough to fit into the 1 inch wide, 5 inches long sample chamber. The sample is placed in the chamber, which is in turn inserted into a Brookfield Thermosel and locked into place with bent needle-nose pliers. The sample chamber has a notch on the bottom that fits the bottom of the Brookfield Thermosel to ensure that the chamber is not allowed to turn when the spindle is inserted and spinning. The sample is heated to 350xc2x0 F., with additional sample being added until the melted sample is about 1 inch below the top of the sample chamber. The viscometer apparatus is lowered and the spindle submerged into the sample chamber. Lowering is continued until brackets on the viscometer align on the Thermosel. The viscometer is turned on, and set to a shear rate which leads to a torque reading in the range of 30 to 60 percent. Readings are taken every minute for about 15 minutes, or until the values stabilize, which final reading is recorded.
When an ultra-low molecular weight ethylene polymer is utilized, it will typically have a density of from 0.850 to 0.970 g/cm3. The density employed will be a function of the end use application contemplated. For instance, when the ultra-low molecular weight ethylene polymer is intended as a wax substitute, densities greater than 0.910, preferably greater than 0.920 g/cm3 will be appropriate. In contrast, when the polymer is intended as to impart some elastomeric characteristics to the composition, densities less than 0.900 g/cm3, preferably less than 0.895 g/cm3 will be appropriate. When the ultra-low molecular weight ethylene polymer is an interpolymer of ethylene and an aromatic comonomer, such as styrene, the density of the interpolymer will be less than 1.10 g/cm3.
Also, preferably the polymeric material used for blending with the rigid hydrogenated block copolymer is characterized as having a percent permanent set of less than 75 at 23xc2x0 C., preferably less than or equal 60 at 23xc2x0 C., more preferably less than or equal to 30 at 23xc2x0 C. and most preferably less than or equal to 15 at 23xc2x0 C. and 38xc2x0 C. and 200 percent strain when measured at a 2 mil thickness using an Instron tensiometer; or preferably a percent set elongation of less than or equal to 25, more preferably 20, most preferably 15 at 23xc2x0 C. and 100 percent strain.
The term xe2x80x9cpolymerxe2x80x9d, as used herein, refers to a polymeric compound prepared by polymerizing monomers, whether of the same or a different type. As used herein, generic term xe2x80x9cpolymerxe2x80x9d embraces the terms xe2x80x9chomopolymer,xe2x80x9d xe2x80x9ccopolymer,xe2x80x9d xe2x80x9cterpolymerxe2x80x9d as well as xe2x80x9cinterpolymer.xe2x80x9d
The term xe2x80x9cinterpolymerxe2x80x9d, as used herein refers to polymers prepared by the polymerization of at least two different types of monomers. As used herein the generic term xe2x80x9cinterpolymerxe2x80x9d includes the term xe2x80x9ccopolymersxe2x80x9d (which is usually employed to refer to polymers prepared from two different monomers) as well as the term xe2x80x9cterpolymersxe2x80x9d (which is usually employed to refer to polymers prepared from three different types of monomers).
The term xe2x80x9chomogeneously branched ethylene polymerxe2x80x9d is used herein in the conventional sense to refer to an ethylene interpolymer in which the comonomer is randomly distributed within a given polymer molecule and wherein substantially all of the polymer molecules have the same ethylene to comonomer molar ratio. The term refers to an ethylene interpolymer that are manufactured using so-called homogeneous or single-site catalyst systems known in the art such Ziegler vanadium, hafnium and zirconium catalyst systems and metallocene catalyst systems e.g., a constrained geometry catalyst systems which is further described herein below.
Homogeneously branched ethylene polymers for use in the present invention can be also described as having less than 15 weight percent, preferably less than 10 weight percent, more preferably less than 5 weight percent and most preferably zero (0) weight percent of the polymer with a degree of short chain branching less than or equal to 10 methyls/1000 carbons. That is, the polymer contains no measurable high density polymer fraction (e.g., there is no fraction having a density of equal to or greater than 0.94 g/cm3), as determined, for example, using a temperature rising elution fractionation (TREF) technique and infrared or 13C nuclear magnetic resonance (NMR) analysis.
Preferably, the homogeneously branched ethylene polymer is characterized as having a narrow, essentially single melting TREF profile/curve and essentially lacking a measurable high density polymer portion, as determined using a temperature rising elution fractionation technique (abbreviated herein as xe2x80x9cTREFxe2x80x9d).
The composition distribution of an ethylene interpolymer can be readily determined from TREF as described, for example, by Wild et al., Journal of Polymer Science, Poly. Phys. Ed., Vol. 20, p. 441 (1982), or in U.S. Pat. Nos. 4,798,081; 5,008,204; or by L. D. Cady, xe2x80x9cThe Role of Comonomer Type and Distribution in LLDPE Product Performance,xe2x80x9d SPE Regional Technical Conference, Quaker Square Hilton, Akron, Ohio, October 1-2, pp. 107-119 (1985).
The composition (monomer) distribution of the interpolymer can also be determined using 13C NMR analysis in accordance with techniques described in U.S. Pat. Nos. 5,292,845; 4,798,081; 5,089,321, incorporated here in by reference, and by J. C. Randall, Rev. Macromol. Chem. Phys., C29, pp. 201-317 (1989).
In analytical temperature rising elution fractionation analysis (as described in U.S. Pat. No. 4,798,081 and abbreviated herein as xe2x80x9cATREFxe2x80x9d), the film or composition to be analyzed is dissolved in a suitable hot solvent (e.g., trichlorobenzene) and allowed to crystallized in a column containing an inert support (stainless steel shot) by slowly reducing the temperature. The column is equipped with both a refractive index detector and a differential viscometer (DV) detector. An ATREF-DV chromatogram curve is then generated by eluting the crystallized polymer sample from the column by slowly increasing the temperature of the eluting solvent (trichlorobenzene). The ATREF curve is also frequently called the short chain branching distribution (SCBD) or composition distribution (CD) curve, since it indicates how evenly the comonomer (e.g., octene) is distributed throughout the sample in that as elution temperature decreases, comonomer content increases. The refractive index detector provides the short chain distribution information and the differential viscometer detector provides an estimate of the viscosity average molecular weight. The composition distribution and other compositional information can also be determined using crystallization analysis fractionation such as the CRYSTAF fractionalysis package available commercially from PolymerChar, Valencia, Spain.
Preferred homogeneously branched ethylene polymers (such as, but not limited to, substantially linear ethylene polymers) have a single melting peak between xe2x88x9230 and 150xc2x0 C., as determined using differential scanning calorimetry (DSC), as opposed to traditional Ziegler polymerized heterogeneously branched ethylene polymers (e.g., LLDPE and ULDPE or VLDPE) which have two or more melting points.
The single melting peak is determined using a differential scanning calorimeter standardized with indium and deionized water. The method involves about 5-7 mg sample sizes, a xe2x80x9cfirst heatxe2x80x9d to about 180xc2x0 C. which is held for 4 minutes, a cool down at 10xc2x0 C./min. to xe2x88x9230xc2x0 C. which is held for 3 minutes, and heat up at 10xc2x0 C./min. to 150xc2x0 C. to provide a xe2x80x9csecond heatxe2x80x9d heat flow vs. temperature curve from which the melting peak(s) is obtained. Total heat of fusion of the polymer is calculated from the area under the curve.
The homogeneously branched ethylene polymers for use in the invention can be either a substantially linear ethylene polymer or a homogeneously branched linear ethylene polymer.
The term xe2x80x9clinearxe2x80x9d as used herein means that the ethylene polymer does not have long chain branching. That is, the polymer chains comprising the bulk linear ethylene polymer have an absence of long chain branching, as in the case of traditional linear low density polyethylene polymers or linear high density polyethylene polymers made using Ziegler polymerization processes (e.g., U.S. Pat. No. 4,076,698 (Anderson et al.)), sometimes called heterogeneous polymers. The term xe2x80x9clinearxe2x80x9d does not refer to bulk high pressure branched polyethylene, ethylene/vinyl acetate copolymers, or ethylene/vinyl alcohol copolymers which are known to those skilled in the art to have numerous long chain branches.
The term xe2x80x9chomogeneously branched linear ethylene polymerxe2x80x9d refers to polymers having a narrow short chain branching distribution and an absence of long chain branching. Such xe2x80x9clinearxe2x80x9d uniformly branched or homogeneous polymers include those made as described in U.S. Pat. No. 3,645,992 (Elston) and those made using so-called single site catalysts in a batch reactor having relatively high ethylene concentrations (as described in U.S. Pat. No. 5,026,798 (Canich) or in U.S. Pat. No. 5,055,438 (Canich)) or those made using constrained geometry catalysts in a batch reactor also having relatively high olefin concentrations (as described in U.S. Pat. No. 5,064,802 (Stevens et al.) or in EP 0 416,815 A2 (Stevens et al.)).
Typically, homogeneously branched linear ethylene polymers are ethylene/xcex1-olefin interpolymers, wherein the xcex1-olefin is at least one C3-C20 xcex1-olefin (e.g., propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene and the like) and preferably the at least one C3-C20 xcex1-olefin is 1-butene, 1-hexene or 1-octene. Most preferably, the ethylene/xcex1-olefin interpolymer is a copolymer of ethylene and a C3-C20 xcex1-olefin, and especially an ethylene/C4-C8 xcex1-olefin copolymer such as an ethylene/1-octene copolymer, ethylene/1-butene copolymer, ethylene/1-pentene copolymer or ethylene/1-hexene copolymer.
Suitable homogeneously branched linear ethylene polymers for use in the invention are sold under the designation of TAFMER(trademark) by Mitsui Chemical Corporation and under the designations of EXACT(trademark) and EXCEED(trademark) resins by Exxon Chemical Company.
The term xe2x80x9csubstantially linear ethylene polymerxe2x80x9d as used herein means that the bulk ethylene polymer is substituted, on average, with about 0.01 long chain branches/1000 total carbons to about 3 long chain branches/1000 total carbons (wherein xe2x80x9ctotal carbonsxe2x80x9d includes both backbone and branch carbons). Preferred polymers are substituted with about 0.01 long chain branches/1000 total carbons to about 1 long chain branches/1000 total carbons, more preferably from about 0.05 long chain branches/1000 total carbons to about 1 long chain branched/1000 total carbons, and especially from about 0.3 long chain branches/1000 total carbons to about 1 long chain branches/1000 total carbons.
As used herein, the term xe2x80x9cbackbonexe2x80x9d refers to a discrete molecule, and the term xe2x80x9cpolymerxe2x80x9d or xe2x80x9cbulk polymerxe2x80x9d refers, in the conventional sense, to the polymer as formed in a reactor. For the polymer to be a xe2x80x9csubstantially linear ethylene polymerxe2x80x9d, the polymer must have at least enough molecules with long chain branching such that the average long chain branching in the bulk polymer is at least an average of from about 0.01/1000 total carbons to about 3 long chain branches/1000 total carbons.
The term xe2x80x9cbulk polymerxe2x80x9d as used herein means the polymer which results from the polymerization process as a mixture of polymer molecules and, for substantially linear ethylene polymers, includes molecules having an absence of long chain branching as well as molecules having long chain branching. Thus a xe2x80x9cbulk polymerxe2x80x9d includes all molecules formed during polymerization. It is understood that, for the substantially linear polymers, not all molecules have long chain branching, but a sufficient amount do such that the average long chain branching content of the bulk polymer positively affects the melt rheology (i.e., the shear viscosity and melt fracture properties) as described herein below and elsewhere in the literature.
Long chain branching (LCB) is defined herein as a chain length of at least one (1) carbon less than the number of carbons in the comonomer, whereas short chain branching (SCB) is defined herein as a chain length of the same number of carbons in the residue of the comonomer after it is incorporated into the polymer molecule backbone. For example, a substantially linear ethylene/1-octene polymer has backbones with long chain branches of at least seven (7) carbons in length, but it also has short chain branches of only six (6) carbons in length.
Long chain branching can be distinguished from short chain branching by using 13C nuclear magnetic resonance (NMR) spectroscopy and to a limited extent, e.g. for ethylene homopolymers, it can be quantified using the method of Randall, (Rev. Macromol.Chem. Phys., C29 (2and3), p. 285-297 (1989)). However as a practical matter, current 13C nuclear magnetic resonance spectroscopy cannot determine the length of a long chain branch in excess of about six (6) carbon atoms and as such, this analytical technique cannot distinguish between a seven (7) carbon branch and a seventy (70) carbon branch. The long chain branch can be as long as about the same length as the length of the polymer backbone.
Although conventional 13C nuclear magnetic resonance spectroscopy cannot determine the length of a long chain branch in excess of six carbon atoms, there are other known techniques useful for quantifying or determining the presence of long chain branches in ethylene polymers, including ethylene/1-octene interpolymers. For example, U.S. Pat. No. 4,500,648, incorporated herein by reference, teaches that long chain branching frequency (LCB) can be represented by the equation LCB=b/Mw wherein b is the weight average number of long chain branches per molecule and Mw is the weight average molecular weight. The molecular weight averages and the long chain branching characteristics are determined by gel permeation chromatography and intrinsic viscosity methods, respectively.
Two other useful methods for quantifying or determining the presence of long chain branches in ethylene polymers, including ethylene/1-octene interpolymers are gel permeation chromatography coupled with a low angle laser light scattering detector (GPC-LALLS) and gel permeation chromatography coupled with a differential viscometer detector (GPC-DV). The use of these techniques for long chain branch detection and the underlying theories have been well documented in the literature. See, e.g., Zimm, G. H. and Stockmayer, W. H., J. Chem. Phys., 17, 1301 (1949) and Rudin, A., Modem Methods of Polymer Characterization, John Wiley and Sons, New York (1991) pp. 103-112.
A. Willem deGroot and P. Steve Chum, both of The Dow Chemical Company, at the Oct. 4, 1994 conference of the Federation of Analytical Chemistry and Spectroscopy Society (FACSS) in St. Louis, Mo., presented data demonstrating that GPC-DV is indeed a useful technique for quantifying the presence of long chain branches in substantially linear ethylene polymers. In particular, deGroot and Chum found that the level of long chain branches in substantially linear ethylene homopolymer samples measured using the Zimm-Stockmayer equation correlated well with the level of long chain branches measured using 13C NMR.
Further, deGroot and Chum found that the presence of octene does not change the hydrodynamic volume of the polyethylene samples in solution and, as such, one can account for the molecular weight increase attributable to octene short chain branches by knowing the mole percent octene in the sample. By deconvoluting the contribution to molecular weight increase attributable to 1-octene short chain branches, deGroot and Chum showed that GPC-DV may be used to quantify the level of long chain branches in substantially linear ethylene/octene copolymers.
DeGroot and Chum also showed that a plot of Log(I2, melt index) as a function of Log(GPC Weight Average Molecular Weight) as determined by GPC-DV illustrates that the long chain branching aspects (but not the extent of long branching) of substantially linear ethylene polymers are comparable to that of high pressure, highly branched low density polyethylene (LDPE) and are clearly distinct from ethylene polymers produced using Ziegler-type catalysts such as titanium complexes and ordinary homogeneous catalysts such as hafnium and vanadium complexes.
For substantially linear ethylene polymers, the empirical effect of the presence of long chain branching is manifested as enhanced rheological properties which are quantified and expressed in terms of gas extrusion rheometry (GER) results and/or melt flow, I10/I2, increases.
The substantially linear ethylene polymers used in the present invention are a unique class of compounds that are further defined in U.S. Pat. No. 5,272,236, application Ser. No. 07/776,130, filed Oct. 15, 1991; U.S. Pat. No. 5,278,272, application Ser No. 07/939,281, filed Sep. 2, 1992; and U.S. Pat. No. 5,665,800, application Ser. No. 08/730,766, filed Oct. 16, 1996, each of which is incorporated herein by reference.
Substantially linear ethylene polymers differ significantly from the class of polymers conventionally known as homogeneously branched linear ethylene polymers described above and, for example, by Elston in U.S. Pat. No. 3,645,992. As an important distinction, substantially linear ethylene polymers do not have a linear polymer backbone in the conventional sense of the term xe2x80x9clinearxe2x80x9d as is the case for homogeneously branched linear ethylene polymers.
Substantially linear ethylene polymers also differ significantly from the class of polymers known conventionally as heterogeneously branched traditional Ziegler polymerized linear ethylene interpolymers (for example, ultra low density polyethylene, linear low density polyethylene or high density polyethylene made, for example, using the technique disclosed by Anderson et al. in U.S. Pat. No. 4,076,698) in that substantially linear ethylene interpolymers are homogeneously branched polymers. Further, substantially linear ethylene polymers also differ from the class of heterogeneously branched ethylene polymers in that substantially linear ethylene polymers are characterized as essentially lacking a measurable high density or crystalline polymer fraction as determined using a temperature rising elution fractionation technique.
The substantially linear ethylene elastomers and plastomers for use in the present invention is characterized as having
(a) melt flow ratio, I10/I2xe2x89xa75.63,
(b) a molecular weight distribution, Mw/Mn, as determined by gel permeation chromatography and defined by the equation:
(Mw/Mn)xe2x89xa6(I10/I2)xe2x88x924.63,
(c) a gas extrusion rheology such that the critical shear rate at onset of surface melt fracture for the substantially linear ethylene polymer is at least 50 percent greater than the critical shear rate at the onset of surface melt fracture for a linear ethylene polymer, wherein the substantially linear ethylene polymer and the linear ethylene polymer comprise the same comonomer or comonomers, the linear ethylene polymer has an I2 and Mw/Mn within ten percent of the substantially linear ethylene polymer and wherein the respective critical shear rates of the substantially linear ethylene polymer and the linear ethylene polymer are measured at the same melt temperature using a gas extrusion rheometer,
(d) a single differential scanning calorimetry, DSC, melting peak between xe2x88x9230xc2x0 and 150xc2x0 C., and
(e) a density less than or equal to 0.865 g/cm3.
Determination of the critical shear rate and critical shear stress in regards to melt fracture as well as other rheology properties such as xe2x80x9cTheological processing indexxe2x80x9d (PI), is performed using a gas extrusion rheometer (GER). The gas extrusion rheometer is described by M. Shida, R. N. Shroff and L. V. Cancio in Polymer Engineering Science, Vol. 17, No. 11, p. 770 (1977) and in Rheometers for Molten Plastics by John Dealy, published by Van Nostrand Reinhold Co. (1982) on pp. 97-99.
The processing index (PI) is measured at a temperature of 190xc2x0 C., at nitrogen pressure of 2500 psig (17.2 MPa) using a 0.0296 inch (752 micrometers) diameter (preferably a 0.0143 inch diameter die for high flow polymers, e.g. 50-100 I2 melt index or greater), 20:1 L/D die having an entrance angle of 180xc2x0. The GER processing index is calculated in millipoise units from the following equation:
PI=2.15xc3x97106 dyne/cm2/(1000xc3x97shear rate),
where: 2.15xc3x97106 dyne/cm2 is the shear stress at 2500 psi (17.2 MPa), and the shear rate is the shear rate at the wall as represented by the following equation:
32Qxe2x80x2/(60 sec/min)(0.745)(Diameterxc3x972.54 cm/in)3, where:
Qxe2x80x2 is the extrusion rate (gms/min),
0.745 is the melt density of polyethylene (gm/cm3), and
Diameter is the orifice diameter of the capillary (inches).
The PI is the apparent viscosity of a material measured at apparent shear stress of 2.15xc3x97106 dyne/cm2.
For substantially linear ethylene polymers, the PI is less than or equal to 70 percent of that of a conventional linear ethylene polymer having an I2, Mw/Mn and density each within ten percent of the substantially linear ethylene polymer.
An apparent shear stress vs. apparent shear rate plot is used to identify the melt fracture phenomena over a range of nitrogen pressures from 5250 to 500 psig (36 to 3.4 MPa) using the die or GER test apparatus previously described. According to Ramamurthy in Journal of Rheology, 30(2), 337-357, 1986, above a certain critical flow rate, the observed extrudate irregularities may be broadly classified into two main types: surface melt fracture and gross melt fracture.
Surface melt fracture occurs under apparently steady flow conditions and ranges in detail from loss of specular gloss to the more severe form of xe2x80x9csharkskinxe2x80x9d. In this disclosure, the onset of surface melt fracture is characterized at the beginning of losing extrudate gloss at which the surface roughness of extrudate can only be detected by 40xc3x97 magnification. The critical shear rate at onset of surface melt fracture for the substantially linear ethylene polymers is at least 50 percent greater than the critical shear rate at the onset of surface melt fracture of a linear ethylene polymer having about the same I2 and Mw/Mn. Preferably, the critical shear stress at onset of surface melt fracture for the substantially linear ethylene polymers of the invention is greater than about 2.8xc3x97106 dyne/cm2.
Gross melt fracture occurs at unsteady flow conditions and ranges in detail from regular (alternating rough and smooth, helical, etc.) to random distortions. For commercial acceptability, (e.g., in blown film products), surface defects should be minimal, if not absent. The critical shear rate at onset of surface melt fracture (OSMF) and critical shear stress at onset of gross melt fracture (OGMF) will be used herein based on the changes of surface roughness and configurations of the extrudates extruded by a GER. For the substantially linear ethylene polymers used in the invention, the critical shear stress at onset of gross melt fracture is preferably greater than about 4xc3x97106 dyne/cm2.
For the processing index determination and for the GER melt fracture determination, substantially linear ethylene polymers are tested without inorganic fillers and do not have more than 20 ppm (parts per million) aluminum catalyst residue. Preferably, however, for the processing index and melt fracture tests, substantially linear ethylene polymers do contain antioxidants such as phenols, hindered phenols, phosphites or phosphonites, preferably a combination of a phenol or hindered phenol and a phosphite or a phosphonite.
The molecular weights and molecular weight distributions are determined by gel permeation chromatography (GPC). A suitable unit is a Waters 150 C high temperature chromatographic unit equipped with a differential refractometer and three columns of mixed porosity where columns are supplied by Polymer Laboratories and are commonly packed with pore sizes of 103, 104, 105 and 106 xc3x85. For ethylene polymers, the unit operating temperature is about 140xc2x0 C. and the solvent is 1,2,4-trichlorobenzene, from which about 0.3 percent by weight solutions of the samples are prepared for injection. Conversely, for the rigid hydrogenated block copolymers, the unit operating temperature is about 25xc2x0 C. and tetrahydrofuran is used as the solvent. A suitable flow rate is about 1.0 milliliters/minute and the injection size is typically about 100 microliters.
For the ethylene polymers where used in the present invention, the molecular weight determination with respect to the polymer backbone is deduced by using narrow molecular weight distribution polystyrene standards (from Polymer Laboratories) in conjunction with their elution volumes. The equivalent polyethylene molecular weights are determined by using appropriate Mark-Houwink coefficients for polyethylene and polystyrene (as described by Williams and Ward in Journal of Polymer Science, Polymer Letters, Vol. 6, p. 621, 1968) to derive the following equation:
Mpolyethylene=a*(Mpolystyrene)b.
In this equation, a=0.4316 and b=1.0. Weight average molecular weight, Mw, is calculated in the usual manner according to the following formula: Mj=(xcexa3 w1(M1J))J. Where w1 is the weight fraction of the molecules with molecular weight M1 eluting from the GPC column in fraction i and j=1 when calculating Mw and j=xe2x88x921 when calculating Mn.
For the at least one homogeneously branched ethylene polymer used in the present invention, the Mw/Mn is preferably less than 3.5, more preferably less than 3.0, most preferably less than 2.5, and especially in the range of from about 1.5 to about 2.5 and most especially in the range from about 1.8 to about 2.3.
Substantially linear ethylene polymers are known to have excellent processability, despite having a relatively narrow molecular weight distribution (that is, the Mw/Mn ratio is typically less than about 3.5). Surprisingly, unlike homogeneously and heterogeneously branched linear ethylene polymers, the melt flow ratio (I10/I2) of substantially linear ethylene polymers can be varied essentially independently of the molecular weight distribution, Mw/Mn. Accordingly, especially when good extrusion processability is desired, the preferred ethylene polymer for use in the present invention is a homogeneously branched substantially linear ethylene interpolymer.
Suitable constrained geometry catalysts for use manufacturing substantially linear ethylene polymers include constrained geometry catalysts as disclosed in U.S. application Ser. No. 07/545,403, filed Jul. 3, 1990; U.S. application Ser. No. 07/758,654, filed Sep. 12, 1991; U.S. Pat. No. 5,132,380 (application Ser. No. 07/758,654); U.S. Pat. No. 5,064,802 (application Ser. No. 07/547,728); U.S. Pat. No. 5,470,993 (application Ser. No. 08/241,523); U.S. Pat. No. 5,453,410 (application Ser. No. 08/108,693); U.S. Pat. No. 5,374,696 (application Ser. No. 08/08,003); U.S. Pat. No. 5,532,394 (application Ser. No. 08/295,768); U.S. Pat. No. 5,494,874 (application Ser. No. 08/294,469); and U.S. Pat. No. 5,189,192 (application Ser. No. 07/647,111), the teachings of all of which are incorporated herein by reference.
Suitable catalyst complexes may also be prepared according to the teachings of WO 93/08199, and the patents issuing therefrom, all of which are incorporated herein by reference. Further, the monocyclopentadienyl transition metal olefin polymerization catalysts taught in U.S. Pat. No. 5,026,798, which is incorporated herein by reference, are also believed to be suitable for use in preparing the polymers of the present invention, so long as the polymerization conditions substantially conform to those described in U.S. Pat. Nos. 5,272,236; 5,278,272 and 5,665,800, especially with strict attention to the requirement of continuous polymerization. Such polymerization methods are also described in PCT/U.S. 92/08812 (filed Oct. 15, 1992).
The foregoing catalysts may be further described as comprising a metal coordination complex comprising a metal of groups 3-10 or the Lanthanide series of the Periodic Table of the Elements and a delocalize xcex2-bonded moiety substituted with a constrain-inducing moiety, said complex having a constrained geometry about the metal atom such that the angle at the metal between the centroid of the delocalized, substituted pi-bonded moiety and the center of at least one remaining substituent is less than such angle in a similar complex containing a similar pi-bonded moiety lacking in such constrain-inducing substituent, and provided further that for such complexes comprising more than one delocalized, substituted pi-bonded moiety, only one thereof for each metal atom of the complex is a cyclic, delocalized, substituted pi-bonded moiety. The catalyst further comprises an activating cocatalyst.
Suitable cocatalysts for use herein include polymeric or oligomeric aluminoxanes, especially methyl aluminoxane, as well as inert, compatible, noncoordinating, ion forming compounds. So-called modified methyl aluminoxane (MMAO) is also suitable for use as a cocatalyst. One technique for preparing such modified aluminoxane is disclosed in U.S. Pat. No. 5,041,584, the disclosure of which is incorporated herein by reference. Aluminoxanes can also be made as disclosed in U.S. Pat. Nos. 5,218,071; 5,086,024; 5,041,585; 5,041,583; 5,015,749; 4,960,878; and 4,544,762, the disclosures of all of which are incorporated herein by reference.
Aluminoxanes, including modified methyl aluminoxanes, when used in the polymerization, are preferably used such that the catalyst residue remaining in the (finished) polymer is preferably in the range of from about 0 to about 20 ppm aluminum, especially from about 0 to about 10 ppm aluminum, and more preferably from about 0 to about 5 ppm aluminum. In order to measure the bulk polymer properties (e.g. PI or melt fracture), aqueous HCl is used to extract the aluminoxane from the polymer. Preferred cocatalysts, however, are inert, noncoordinating, boron compounds such as those described in EP 520732.
Substantially linear ethylene are produced via a continuous (as opposed to a batch) controlled polymerization process using at least one reactor (e.g., as disclosed in WO 93/07187, WO 93/07188, and WO 93/07189), but can also be produced using multiple reactors (e.g., using a multiple reactor configuration as described in U.S. Pat. No. 3,914,342, the disclosure of which is incorporated herein by reference) at a polymerization temperature and pressure sufficient to produce the interpolymers having the desired properties. The multiple reactors can be operated in series or in parallel, with at least one constrained geometry catalyst employed in at least one of the reactors.
Substantially linear ethylene polymers can be prepared via the continuous solution, slurry, or gas phase polymerization in the presence of a constrained geometry catalyst, such as the method disclosed in EP 416,815-A. The polymerization can generally be performed in any reactor system known in the art including, but not limited to, a tank reactor(s), a sphere reactor(s), a recycling loop reactor(s) or combinations thereof and the like, any reactor or all reactors operated partially or completely adiabatically, nonadiabatically or a combination of both and the like. Preferably, a continuous loop-reactor solution polymerization process is used to manufacture the substantially linear ethylene polymer used in the present invention.
In general, the continuous polymerization required to manufacture substantially linear ethylene polymers may be accomplished at conditions well known in the prior art for Ziegler-Natta or Kaminsky-Sinn type polymerization reactions, that is, temperatures from 0 to 250xc2x0 C. and pressures from atmospheric to 1000 atmospheres (100 MPa). Suspension, solution, slurry, gas phase or other process conditions may be employed if desired.
A support may be employed in the polymerization, but preferably the catalysts are used in a homogeneous (i.e., soluble) manner. It will, of course, be appreciated that the active catalyst system forms in situ if the catalyst and the cocatalyst components thereof are added directly to the polymerization process and a suitable solvent or diluent, including condensed monomer, is used in said polymerization process. It is, however, preferred to form the active catalyst in a separate step in a suitable solvent prior to adding the same to the polymerization mixture.
The substantially linear ethylene polymers used in the present invention are interpolymers of ethylene with at least one C3-C20 xcex1-olefin and/or C4-C18 diolefin. Copolymers of ethylene and an xcex1-olefin of C3-C20 carbon atoms are especially preferred. The term xe2x80x9cinterpolymerxe2x80x9d as discussed above is used herein to indicate a copolymer, or a terpolymer, or the like, where, at least one other comonomer is polymerized with ethylene or propylene to make the interpolymer.
Suitable unsaturated comonomers useful for polymerizing with ethylene include, for example, ethylenically unsaturated monomers, conjugated or non-conjugated dienes, polyenes, etc. Examples of such comonomers include C3-C20 xcex1-olefins such as propylene, isobutylene, 1-butene, 1-hexene, 1-pentene, 4-methyl-1-pentene, 1-heptene, 1-octene, 1-nonene, 1-decene, and the like. Preferred comonomers include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, and 1-octene, and 1-octene is especially preferred. Other suitable monomers include styrene, halo- or alkyl-substituted styrenes, vinylbenzocyclobutane, 1,4-hexadiene, 1,7-octadiene, and naphthenics (e.g., cyclopentene, cyclohexene and cyclooctene).
In one embodiment, the composition used in the present invention comprises at least one rigid hydrogenated block copolymer and at least one polypropylene polymer. Suitable polypropylene polymers for use in the invention, including random block propylene ethylene polymers, are available from a number of manufacturers, such as, for example, Montell Polyolefins and Exxon Chemical Company. At Exxon, suitable polypropylene polymers are supplied under the designations ESCORENE(trademark) and ACHIEVE(trademark).
Suitable poly lactic acid (PLA) polymers for use in the invention are well known in the literature (e.g., see D. M. Bigg et al., xe2x80x9cEffect of Copolymer Ratio on the Crystallinity and Properties of Polylactic Acid Copolymersxe2x80x9d, ANTEC ""96, pp. 2028-2039; WO 90/01521; EP 0 515203A; and EP 0 748846A2). Suitable poly lactic acid polymers are supplied commercially by Cargill Dow under the designation EcoPLA(trademark).
Suitable thermoplastic polyurethane polymers for use in the invention are commercially available from The Dow Chemical Company under the designation PELLATHANE(trademark).
Suitable polyolefin carbon monoxide interpolymers can be manufactured using well known high pressure free-radical polymerization methods. However, they may also be manufactured using traditional Ziegler-Natta catalysis and even with the use of so-called homogeneous catalyst systems such as those described and referenced herein above.
Suitable free-radical initiated high pressure carbonyl-containing ethylene polymers such as ethylene acrylic acid interpolymers can be manufactured by any technique known in the art including the methods taught by Thomson and Waples in U.S. Pat. No. 3,520,861 and by McKinney et al. in U.S. Pat. Nos. 4,988,781; 4,599,392; and 5,384,373, the disclosures of which are incorporated herein by reference.
Suitable ethylene vinyl acetate interpolymers for use in the invention are commercially available from various suppliers, including Exxon Chemical Company and E.I. du Pont de Nemours and Company.
Suitable ethylene/alkyl acrylate interpolymers are commercially available from various suppliers. Suitable ethylene/acrylic acid interpolymers are commercially available from The Dow Chemical Company under the designation PRIMACOR(trademark). Suitable ethylene/methacrylic acid interpolymers are commercially available from E.I. du Pont de Nemours and Company under the designation NUCREL(trademark).
Suitable polyethylene terephthalate polymers include LIGHTER(trademark) available from The Dow Chemical Company.
Chlorinated polyethylene (CPE), especially chlorinated substantially linear ethylene polymers, can be prepared by chlorinating polyethylene in accordance with well known techniques. Preferably, chlorinated polyethylene comprises equal to or greater than 30 weight percent chlorine. Suitable chlorinated polyethylenes for use in the invention are commercially supplied by Dupont Dow Elastomers L.L.C under the designation TYRIN(copyright).
Suitable polycarbonates are commercially available from various suppliers, including The Dow Chemical Company under the designation CALIBRE(copyright).
Suitable polyamids, such as nylon are commercially available from various suppliers, including ZYTEL(trademark) available from DuPont, CAPRON(trademark) available from Allied and ULTAMID(trademark) available from BASF.
Suitable polyethers are commercially available from various suppliers, including ULTEM(trademark) available from GE Plastics.
Suitable poly/vinyl choride polymers are commercially available from various suppliers, including ALPHA DURAL(trademark) AND ALPHA available from Alpha Chemical and Plastics, UNICHEM(trademark) available from Colorite Plastics, GEON(trademark) available from B.F. Goodrich.
Suitable poly/vinylidene chloride polymers are commercially available from various suppliers, including SARAN(trademark) available from The Dow Chemical Company.
Suitable polyesters are commercially available from various suppliers, including FIBERCORE(trademark) available from American Cyanamid; AROPOL(trademark) available from Ashland Chemical Company and COREZYN(trademark) available from Interplastic.
Suitable non-hydrogenated styrene-butadiene block copolymers are commercially available from various suppliers, including Dexco under the designation Vector(trademark). Additionally, partially hydrogenated block copolymers can also be used and are well known in the art. Such polymers are easily prepared using hydrogenation catalysts well known in the art. Partially hydrogenated block copolymers include block copolymers having up to 100 percent diene unsaturation and 0 to less than 90 percent aromatic hydrogenation.
Suitable styrenic polymers include syndiotactic and atactic polystyrenes and high impact polystyrene resins which are commercially available from various suppliers, including QUESTRA(copyright), STYRON(copyright) and STYRON-A-TECH(copyright), available from The Dow Chemical Company.
Suitable ABS resins are commercially available from various suppliers, including MAGNUM(copyright) available from The Dow Chemical Company.
Suitable ABS/PC compositions are commercially available from various suppliers, including PULSE(copyright) available from The Dow Chemical Company.
Suitable SAN copolymers are commercially available from various suppliers, including TYRIL(copyright) available from The Dow Chemical Company.
Suitable ethylene vinyl alcohol copolymers are commercially available from various suppliers, including-ELVANOL(trademark) which is available from DuPont and EVA polymers available from Eval Company of America.
Suitable epoxy resins are commercially available from various suppliers, including D.E.R. resins and D.E.N. resins available from The Dow Chemical Company.
Suitable cyclic-olefin-polymers and copolymers are polymerized cycloolefin monomers exemplified by norbornene-type polymers such as are described in U.S. Pat. Nos. 5,115,041, 5,142,007, 5,143,979, all of which are incorporated herein by reference. The cycloolefin moiety may be substituted or unsubstituted. Suitable cycloolefin monomers include substituted and unsubstituted norbornenes, dicyclopentadienes, dihydrodicyclopentadienes, trimers of cyclopentadiene, tetracyclododecenes, hexacycloheptadecenes, ethylidenyl norbornenes and vinylnorbornenes. Substituents on the cycloolefin monomers include hydrogen, alkyl alkenyl, and aryl groups of 1 to 20 carbon atoms and saturated and unsaturated cyclic groups of 3 to 12 carbon atoms which can be formed with one or more, preferably two, ring carbon atoms. The substituents on the cycloolefin monomers can be any which do not poison or deactivate the polymerization catalyst. Examples of preferred monomers include but are not limited to dicyclopentadiene, methyltetracyclo-dodecene, 2-norbornene, and other norbornene monomers such as 5-methyl-2-norbornene, 5,6-dimethyl-2-norbornene, 5-ethyl-2-norbornene, 5-ethylidenyl-2-norbornene, 5-butyl-2-norbornene, 5-hexyl-2-norbornene, 5-octyl-2-norbornene, 5-phenyl-2-norbornene, 5-dodecyl-2-norbornene, 5-isobutyl-2-norbornene, 5-octadecyl-2-norbornene, 5-isopropyl-2-norbornene, 5-p-toluyl-2-norbornene, 5-xcex1-naphthyl-2-norbornene, 5-cyclohexyl-2-norbornene, 5-isopropenyl-2-norbornene, 5-vinyl-2-norbornene, 5,5-dimethyl-2-norbornene, tricyclopentadiene (or cyclopentadiene trimer), tetracyclopentadiene (or cyclopentadiene tetramer), dihydrodicyclopentadiene (or cyclopentene-cyclopentadiene co-dimer), methyl-cyclopentadiene dimer, ethyl-cyclopentadiene dimer, tetracyclododecene 9-methyl-tetracyclo[6,2,1,13,6O2,7]dodecene-4, (or methyl-tetracyclododecene), 9-ethyl-tetracyclo[6,2,1,13,6O2,7]dodecene-4, (or ethyl-tetracyclododecene), 9-hexyl-tetracyclo-[6,2,1,13,6O2,7]dodecene-4,9-decyl-tetracyclo[6,2,1,13,6O2,7]dodecene-4,9-decyl-tetracyclo[6,2,1,13,6O2,7]dodecene-4,9,10-dimethyl-tetracyclo[6,2,1,13,6O2,7]dodecene-4,9-methyl-10-ethyl-tetracyclo[6,2,1,13,6O2,7]dodecene-4,9-cyclohexyl-tetracyclo [6,2,1,13,6O2,7]dodecene-4,9-chloro-tetracyclo[6,2,1,13,6O2,7]dodecene-4,9-bromo-tetracyclo[6,2,1,13,6O2,7]-dodecene-4,9-fluoro-tetracyclo[6,2,1,13,6O2,7]dodecene-4,9-isobutyl-tetracyclo-[6,2,1,13,6O2,7]dodecene-4, and 9,10-dichlorotetracyclo[6,2,1,13,6O2,7]-dodecene-4.
Polymers comprising two or more different types of cyclic olefin monomeric units are also suitable. For example, copolymers of methyltetracyclododecane (MTD) and methylnorbornene (MNB) are especially suitable. More preferably, the polymers comprise three or more different types of monomeric unites, e.g., terpolymers, including MTD, MNB and dicyclopentadiene (DCPD).
Additionally, hydrogenated vinyl aromatic homopolymers can be used in combination with the hydrogenated block copolymers. Hydrogenated vinyl aromatic homopolymers typically have high aromatic hydrogenation levels as well (greater than 80, preferably greater than 90 percent). Other hydrogenated vinyl aromatic/conjugated diene block copolymers can also be used, provided that it is a different polymer than the hydrogenated block copolymer selected in I).
Any polymeric material which will enhance the properties of a hydrogenated block copolymer or be enhanced by the presence of a hydrogenated block copolymer is useful in the compositions utilized in the present invention.
Optionally, compatibilizers may also be used in the composition of the present invention. A compatibilizer typically contains a functional group which is compatible with the hydrogenated block copolymer and an additional functional group which is compatible with the other synthetic or natural polymer. Compatibilizers are well known in the art and one skilled in the art would easily be able to recognize the type of compatibilizer suitable for the desired compositions, if needed. For example, a blend of a hydrogenated rigid block copolymer with a styrene-butadiene-styrene block copolymer or other styrenic polymer may additionally comprise a styrene-ethylenebutene-styrene block copolymer as a compatibilizer. Additionally, a blend of a hydrogenated rigid block copolymer with a polycarbonate may additionally comprise a polyamide-maleic anhydride grafted polyethylene as a compatibilizer
The polymer blend compositions used in the present invention typically contain from 0.5, generally from 1, preferably from 3, more preferably from 5 and most preferably from 10 to 99.5, generally to 99, preferably to 97, more preferably to 95 and most preferably to 90 weight percent of the rigid hydrogenated block copolymer based on the total weight of the composition.
In one embodiment, the additional polymer comprises from 5, typically from 10, generally from 15, preferably from 25, more preferably from 30 and most preferably from 40 to 95, typically to 90, generally to 85, preferably to 75, more preferably to 70 and most preferably to 60 weight percent of the composition comprising the hydrogenated rigid block copolymer.
In one embodiment of the present invention, the composition comprises more than one hydrogenated block copolymer. The composition may comprise a flexible hydrogenated block copolymer or another rigid hydrogenated block copolymer. A flexible hydrogenated block copolymer is defined as having at least two distinct blocks of hydrogenated polymerized vinyl aromatic monomer, herein referred to as hydrogenated vinyl aromatic polymer blocks, and at least one block of hydrogenated polymerized conjugated diene monomer, herein referred to as hydrogenated conjugated diene polymer block, and is further characterized by:
a) a weight ratio of hydrogenated conjugated diene polymer block to hydrogenated vinyl aromatic polymer block of greater than 40:60;
b) a total number average molecular weight (Mnt) of from 30,000 to 150,000, wherein each hydrogenated vinyl aromatic polymer block (A) has a Mna of from 5,000 to 45,000 and each hydrogenated conjugated diene polymer block (B) has a Mnb of from 12,000 to 110,000; and
c) a hydrogenation level such that each hydrogenated vinyl aromatic polymer block has a hydrogenation level of greater than 90 percent and each hydrogenated conjugated diene polymer block has a hydrogenation level of greater than 95 percent.
The compositions of rigid hydrogenated block copolymer and additional polymeric material may be prepared by any suitable means known in the art such as, but not limited to, dry blending in a pelletized form in the desired proportions followed by melt blending in a screw extruder, Banbury mixer or the like. The dry blended pellets may be directly melt processed into a final solid state article by, for example, injection molding. Additionally, the compositions may be prepared by solution mixing the individual polymeric components.
Additives such as antioxidants (for example, hindered phenols such as, for example, Irganox(copyright) 1010), phosphites (for example, Irgafos(copyright) 168)), U. V. stabilizers, to cling additives (for example, polyisobutylene), antiblock additives, slip agents, colorants, pigments, fillers, fire retardants, light and heat stabilizers, extension oils and the like can also be included in the compositions of the present invention, to the extent that they do not interfere with the enhanced properties discovered by applicants. In-process additives, e.g. calcium stearate, water, and fluoropolymers may also be used for purposes such as for the deactivation of residual catalyst or for further improved processability.
In another aspect of the present invention, rigid hydrogenated block copolymers, or blends thereof can also be used in the form of aqueous dispersions for use in coatings and dipped articles. Such dispersions will comprised the hydrogenated rigid block copolymer, optional blended polymers, water and surfactant(s). Such dispersions can be produced using conventional batch or continuous processes such as phase inversion or direct dispersion techniques, known to those skilled in the art.
Additionally, high internal phase ratio (HIPR) emulsions, as described in U.S. Pat. No. 5,539,021, incorporated herein by reference, can be produced by continuously merging into a disperser, in the presence of an emulsifying and a stabilizing amount of a surfactant, a continuous phase liquid stream having a flow rate R1, and a disperse phase liquid stream having a flow rate R2; mixing the merged streams with a sufficient amount of shear, with R2:R1 sufficiently constant, to form the HIPR emulsion without phase inversion or stepwise distribution of an internal phase into an external phase; wherein R2:R1 is in a range where the polydispersity of the high internal phase ratio emulsion is less than 2.
The continuous phase and disperse phase liquid streams are sufficiently immiscible with each other to be emulsifiable. In one aspect R2:R1 is defined by a range where the polydispersity of the particles of the HIPR emulsion is less than 2. The term polydispersity is,used to denote the ratio of the volume average diameter and the number average diameter of the particles, or Dv/Dn.
Preferably R2:R1 is such that the polydispersity is less than 1.5, more preferably less than 1.2, and most preferably not greater than 1. The allowable variance of the rates of each stream depends, in part, on the nature of the disperse and continuous phases, and the dispe4rswers used to make the HIPR emulsion. Preferably this variance is not greater than 10, more preferably not greater than 5, and most preferably less than 1 percent. Preferably, the average particle size of the HIPR emulsion is less than about 2 microns, more preferably, less than 1 micron.
The continuous phase and the disperse phase are liquids that are sufficiently immiscible to form a stable emulsion in the presence of a sufficient quantity of a surfactant. The liquid may be neat, molten, or a solid or unpumpable liquid dissolved in a solvent.
Preferably, the continuous phase is aqueous and the disperse phase comprises the hydrogenated rigid block copolymer, and optionally a solvent. Suitable solvents include those used in the production of the hydrogenated block copolymer as taught herein.
Suitable surfactants include anionic, cationic, nonionic, or combinations thereof. Generally, higher surfactant concentrations result in smaller diameter particles, but surfactant concentrations that are too high tend to deleteriously affect the properties of the final product made from the emulsion. Typically surfactant concentrations are in the range of 0.1, more preferably 0.5, and most preferably 2, to about 15, preferably to about 8, more preferably to about 6 and most preferably about 4 weight percent, based on the weight of the dispersed polymer. The surfactant may be added initially to either the continuous phase or the disperse phase prior to mixing of the two phases, or added separately to the mixing device as a third stream. The surfactant is preferably added initially with the disperse phase prior to mixing of the two phases.
Of particular interest are the class of surfactants comprising the alkali or amine fatty acid salts such as alkali metal oleates (sodium oleate) and stearates; polyoxyethylene nonionics; alkali metal lauryl sulfates, quaternary ammonium surfactants; alkali metal alkylbenzene sulfonates, such as sodium dodecylbenzene sulfonate; and alkali metal soaps of modified resins.
Typically the dispersion produced contains a concentration of dispersed phase in amounts up to about 60 percent solids in order to have viscosities that are reasonable for processing. Continuous processes, such as in U.S. Pat. No. 5,539,021 will produce higher solids concentrations, but are typically diluted before use.
Examples of continuous processes suitable for the formation of these aqueous dispersions include U.S. Pat. Nos. 4,123,403; 5,539,021 and 5,688,842, all of which are incorporated herein by reference.
A latex is prepared from an HIPR emulsion by combining the emulsion with a suitable amount of the liquid which constitutes the continuous phase liquid, or a liquid which is compatible with the continuous phase, but which does not interfere with the integrity of the particles. Where water is the continuous phase, the latex is prepared by adding water to the HIPR emulsion. More preferably, the latex is made in a continuous fashion by directing the HIPR emulsion and water through any suitable dilution unit, such as a centrifugal pump-head.
Rigid hydrogenated block copolymer compositions have various advantages including excellent impact properties and chemical resistance. The following end-use applications advantageously utilize such rigid hydrogenated block copolymers and blends thereof.
One aspect of the present invention is related to films produced from a composition comprising a rigid hydrogenated block copolymer. The films can be monolayer or multilayer films as well as uniaxial, biaxial and multiaxial oriented films. The film typically has a thickness of less than 20 mils. Such films include, but are not limited to, cast films such as capacitor films, key pads, uniaxially oriented film, weatherable film, labels, release liners, envelope window film, box/carton window film, medical packaging film, film sheet, trays, graphic art films, membrane switches, blister packaging for food and pharmaceuticals and UV protection films, blown films such as biaxially oriented films and solvent cast films.
Methods of producing films from polymeric materials are well known in the art and described in Plastics Engineering Handbook of the Society of the Plastics Industry, Inc., Fourth Edition, 1976, pages 156, 174, 180 and 183.
Another aspect of the present invention is related to sheet produced from a composition comprising a rigid hydrogenated block copolymer. Sheet typically has a thickness of 20 mils or more. Rigid hydrogenated block copolymer sheet can be used to produce products which include, but are not limited to, automotive glazing, architectural glazing, point of purchase displays, machine guards, ceiling light panels, solar collectors, flat panel displays, basketball backboards, wind screens, bug deflectors, sun roofs, signage, protective sheet (such as boards used in hockey rinks), and the like. Additionally, sheet can be thermoformed to produce articles such as containers and the like.
Methods of producing sheet from polymeric materials are well known in the art and include extrusion, and calendering, all of which are described in Plastics Engineering Handbook of the Society of the Plastics Industry, Inc., Fourth Edition, 1976, on pages 183, 348, and 357.
Additional applications of film and sheet include microwaveable sheet and packaging, thermoformed cups/containers, sunroofs, containers and trays for food, liquid crystal display substrates, rear projection TV screens, beverage machine covers, labels, architectural and greenhouse glazing, bug deflectors and side wind screens, microwave or appliance doors, coatings, films or protective cap layers for improved surface hardness, scratch or abrasion resistance, surface luster and transparency; graphic arts film, laser-readable parcel window film, index tabs, pharmaceutical packaging, solar cell covers, heat sealable films, photosensitive films, weatherable film or sheet, electrical and capacitor films, transparency films, barrier films, window films, steam sterilization film, recreational vehicle exteriors, boat/marine exterior components such as transparent hatches, camper tops and outdoor signage.
The films and sheet may be monolayer or multilayer in structure. Additional layers may be other polymeric materials including, but not limited to those polymers to listed as possible polymers for blending with the rigid hydrogenated block copolymers.
Another aspect of the present invention is related to extruded profiles produced from a composition comprising a rigid hydrogenated block copolymer. Such profiles include, but are not limited to, window blinds and wand profiles, roofing products, exterior trim, window trim, tubing, pipe, rods, fluorescent light tubes, packaging, plastic lumber and the like.
Methods of producing profiles from polymeric materials are well known in the art and described in Plastics Engineering Handbook of the Society of the Plastics Industry, Inc., Fourth Edition, 1976, page 191.
Another aspect of the present invention is related to fibers produced from a composition comprising a rigid hydrogenated block copolymers. Such fibers include, but are not limited to, electronic optic fibers, fiber glass applications, fiber reinforcement, filter media, textiles, nonwovens, yarns and the like.
Methods of producing fibers from polymeric materials are well known in the art and include spunbond fibers or melt blown fibers as disclosed in U.S. Pat. Nos. 25 4,340,563; 4,663,220; 4,668,566; or 4,322,027, gel spun fibers disclosed in U.S. Pat. No. 4,413,110, and fabrics produced therefrom which is disclosed in U.S. Pat. No. 3,485,706, all of which are incorporated herein by reference.
Another aspect of the present invention is related to coated articles produced from a composition comprising a rigid hydrogenated block copolymer. Coated articles include extrusion coated articles and aqueous dispersion coated articles, coated fabric, coated inorganic materials such as concrete, glass and the like, coated paper or cardboard, coated wood products, and coated metal products. Examples include carpet backing, awnings, shading fabric, indoor and outdoor sun screens, wall coverings, food packaging, microporous waterproof wovens, tent fabrics, and caravan extensions, garden furniture garments, safety and protective wovens, films, fibers, apparel, bandages, and the like. Additionally, the rigid hydrogenated block copolymers can also be used in paint formulations. Alternatively, coating products can be produced using a spin coating process, wherein the rigid hydrogenated block copolymer is spin coated onto a mold to produce an article; such as spin coating an optical media disc or spin coating onto an optical media disc. Additionally, dipped products can also be made using coatings of the hydrogenated block copolymer. In particular, dipped goods can be produced using aqueous dispersions of the hydrogenated block copolymer or blends thereof.
Methods of coating with polymeric materials are well known in the art and include extrusion, solvent casting, and coating from aqueous dispersion/emulsions, all of which are described in Plastics Engineering Handbook of the Society of the Plastics Industry, Inc., Fourth Edition, 1976, on pages 185, and spin coating as described in U.S. Pat. Nos. 5,635,114; 5,468,324; and 5,663,016, which are incorporated herein by reference.
Another aspect of the present invention is related to injection molded articles produced from a composition comprising a rigid hydrogenated block copolymer. Injection molded articles include, but are not limited to, refrigerator shelving and crisper drawers, blenders, lenses for automotive applications such as headlamps and instrument panels, reusable flatware, tumblers, pitchers, toothbrush and hairbrush handles, tool handles, housewares, industrial lighting lenses such as HID (high intensity discharge), fluorescent and incandescent lenses, medical labware, syringes, optical devices such as industrial and opthamalic precision lenses, light guides, prisms, lenses, laser printer lenses, transparent cover for outdoor instruments and gages, optical mirrors, optical lenses, diffraction lenses, optical filters, CD pickup lenses, laser waveguides, camera lenses, contact lenses, commercial/residential/industrial lenses, labware, test tubes, pipettes, syringes, catheters, flasks, beakers, sterilization containers, pharmaceutical packaging, optical fiber connectors, auto interior and exterior lenses including center high mount stop-lamps, dome lights, courtesy lamp lenses, light distribution systems and the like.
Methods of injection molding with polymeric materials are well known in the art and are described in Plastics Engineering Handbook of the Society of the Plastics Industry, Inc., Fourth Edition, 1976, on page 83.
Another aspect of the present invention is related to rotational molded articles, which include large articles such as toys (hobbyhorses, dolls, sandboxes, small swimming pools, and athletic balls), containers, light globes, storage tanks, furniture, carboys, bottles, shipping containers, business and recreational furniture, planters, trash containers, whirlpool tubs, light globes, boats, canoes, camper tops, advertising display signs, racks, mannequins and the like.
Methods of rotational molding and rotational/slush molding are described in Plastics Engineering Handbook of the Society of the Plastics Industry, Inc., Fourth Edition, 1976, page 348.
Another aspect of the present invention is related to blow molded articles produced from a composition comprising a rigid hydrogenated block copolymer. Blow molded articles include, but are not limited to, extruded bottles, injection molding bottles such as baby bottles and medical use bottles, water tanks, air ducts, hollow industrial parts, seat backs, fluid reservoirs, stadium seating, structural covers for office equipment, and the like.
Methods of blow molding with polymeric materials are well known in the art and are described in Plastics Engineering Handbook of the Society of the Plastics Industry, Inc., Fourth Edition, 1976, on page 326.
Another aspect of the present invention is related to pultruded articles produced from a composition comprising a rigid hydrogenated block copolymer. Pultruded articles are continuous, cross-sectional, composite, extruded profiles produced by extruding a polymer melt and continuous fiber, simultaneously, through the same profile die. structural beams, reinforcement bar, barricades, composite pipe, automotive bumper moldings, concrete reinforcement, window/door lineals, wood reinforcement, glulam (laminated joists) and the like.
Methods of pultrusion with polymeric materials are well known in the art and are described in Plastics Engineering Handbook of the Society of the Plastics Industry, Inc., Fourth Edition, 1976, on page 47.
All end-use applications can be provided as monolayer or multilayer articles, wherein any layer comprises the hydrogenated block copolymer as described herein. Additional layers may be other polymeric materials including, but not limited to those polymers listed as possible polymers for blending with the rigid hydrogenated block copolymers.
Surprisingly, these highly hydrogenated copolymers are capable of making a wide range of transparent (translucent or opaque with colorants), low color, rigid films; profiles; sheets; coated, injection molded, and blow molded articles having excellent properties at standard and elevated temperatures. The copolymers offer low residuals and extractables, high strength, good thermal, radiation, and light resistance, resistance to polar chemicals, acids, and bases, and retention of properties at elevated temperatures. In addition, these copolymers can be processed without drying, are compatible with other polyolefins, and have low health, environmental and safety concerns.
The following examples are provided to further illustrate and illuminate the present invention but are not intended to limit the invention to the specific embodiments set forth.